add method to get underlying executable (#2630)

* add method to get underlying executable

* Copy the function because copy cleans up the graph linkage/users

* style

src/ngraph/runtime/hybrid/hybrid_executable.cpp

@@ -36,10 +36,14 @@ runtime::hybrid::HybridExecutable::HybridExecutable(
     const shared_ptr<Function>& func,
     bool enable_performance_collection,
     bool debug_enabled)
-    : m_function{func}
+    : m_function{clone_function(*func)}
     , m_backend_list{backend_list}
     , m_debug_enabled{debug_enabled}
 {
+    if (backend_list.size() == 0)
+    {
+        throw runtime_error("Hybrid Executable constructed with zero-sized backend list");
+    }
     // Run placement pass
     ngraph::pass::Manager pass_manager;
     pass_manager.register_pass<runtime::hybrid::pass::DefaultPlacement>(m_backend_list);

src/ngraph/runtime/hybrid/hybrid_executable.hpp

@@ -31,8 +31,8 @@ namespace ngraph
         {
             class HybridExecutable;
         }
-    }
-}
+    } // namespace runtime
+} // namespace ngraph
 
 class ngraph::runtime::hybrid::HybridExecutable : public runtime::Executable
 {
@@ -45,6 +45,12 @@ public:
     bool call(const std::vector<std::shared_ptr<ngraph::runtime::Tensor>>& outputs,
               const std::vector<std::shared_ptr<ngraph::runtime::Tensor>>& inputs) override;
 
+    template <typename T>
+    std::shared_ptr<T> get_as() const
+    {
+        return std::dynamic_pointer_cast<T>(m_executable);
+    }
+
 private:
     std::shared_ptr<ngraph::Function> m_function;
     std::shared_ptr<Executable> m_executable;